Two-stage solenoid valve for an electropneumatic valve control unit

ABSTRACT

The invention relates to a two-stage solenoid valve for an electropneumatic valve control unit, particularly a pilot control unit of a pressure modulator. Said solenoid valve at least comprises a solenoid system ( 6 ) to which a first and second current intensity can be applied as well as a solenoid valve device ( 8 ) that is accommodated in the solenoid system ( 6 ) and is provided with a primary side ( 8   a ) to be connected to a first compressed-air supply and a secondary side ( 8   b ) to be connected to a second compressed-air supply. A primary valve ( 10 ) encompassing an adjustable primary armature ( 10   a ) that is biased by means of a primary armature spring ( 10   c ) is provided on the primary side, while a secondary valve ( 11 ) encompassing an adjustable secondary armature ( 11   a ) which is biased by means of a secondary armature spring ( 11   c ) is provided on the secondary side. The solenoid valve device ( 8 ) is embodied as a valve cartridge which is to be inserted from one side. Advantageously, the diameters or a forward zone ( 18   a ) and a central zone ( 18   c ) of the valve cartridge ( 8 ) are smaller than or identical to the diameter of a rear zone of the valve cartridge, “forward” being in relation to the direction of insertion.

The present invention generally relates to a two-stage solenoid valvefor an electropneumatic valve control unit, especially, for a pilotcontrol unit of a pressure modulator.

A solenoid valve of this type may be provided, in particular, in thepilot control unit of a brake modulator, which, with its solenoidvalves, activates an air-flow-boosting relay valve, which, in turn, canactivate one or more ducts. For use in an electropneumatic brake system,such as an electronically regulated brake system (EBS) for vehicletrailers, wheel brake modules having brake cylinders for the wheelbrakes are activated by the relay valve.

DE 10 2004 035 763 A1 describes a solenoid valve of the general typeunder consideration, which is provided as the valve control unit for twobrake ducts of an electropneumatic brake system. An air admission valvehaving a primary armature and a vent valve having a secondary armatureare provided in one valve unit, the two magnet armatures having a commonarmature guide arrangement and a common solenoid system and beingswitched at different current intensities. Thus, air can be admitted tothe downstream wheel module, the input pressure can be held and ventingcan be achieved by means of a common solenoid system.

The two-stage solenoid valve of DE 10 2004 035 763 A1 is assembled fromboth sides into the housing of the pilot control unit. Thus, armatureshaving an armature spring, armature guide tube with core and valve seat,respectively, are introduced from the primary or secondary side,respectively, into the common coil. The respective cores are pressedtogether in the middle. Closing elements fix the frame interiors of thesolenoid systems of the plurality of valve units.

DE 100 09 116 A1 describes a valve device for the pilot control unit ofa brake pressure modulator in a trailer having an electronic brakesystem. The solenoid valves are constructed as cartridge solenoidvalves, with the valve cartridge placed in a housing having a solenoid.First, this solenoid is introduced into the housing, and then the valvecartridge is inserted into and joined to the housing.

It is an object of the present invention to provide a two-stage solenoidvalve for an electropneumatic control unit, which valve permits saferoperation and rapid, simple assembly.

This object is achieved by a solenoid valve according to claim 1. Thedependent claims describe preferred embodiments.

In accordance with embodiments of the present invention, a valvecartridge is provided that, by virtue of its cross section, which tapersto one side, can be introduced from one side. The valve cartridge can beinserted, in particular, as a stepped body into the magnet system,together with housed movable parts, such as, for example, armatures andsprings.

The present invention offers several advantages.

The valve cartridge requires little space, is inexpensive and,advantageously, has low susceptibility to improper assembly.

Assembly from one side is possible, with simple options for fasteningthe magnet internals. Thereby, the receiving housing, such as, forexample, a pilot control unit, is simpler.

Pre-assembled and pre-tested units can be built in. Thus, repair is alsomade easier.

Thermal expansion of the surrounding housing has no influence on thestroke tolerances and the armature forces.

Compared with conventional split cores, the one-piece core has theadvantage that the magnetic flux is not hindered by a compression joint.The magnetic behavior remains constant over the number of pieces.

Exemplary embodiments of the present invention will be described ingreater detail hereinafter on the basis of the accompanying drawings,wherein:

FIG. 1 is an axial sectional view taken through a valve cartridge of asolenoid valve in accordance with an embodiment of the presentinvention;

FIG. 2 is an axial sectional view taken through a solenoid valve withvalve cartridge and solenoid in accordance with an embodiment of thepresent invention; and

FIG. 3 is a sectional view taken through a pilot control unit containinga solenoid valve in accordance with an embodiment of the presentinvention.

A solenoid valve 1 is provided for introduction into a pilot controlhousing 2 illustrated in FIG. 3. In pilot control housing 2, at leastone valve bore 4 is provided, which extends in transverse direction froma side face 2 c and which, according to embodiments of the presentinvention, can be formed as a blind bore, so that the opposite side face2 d can be closed. Alternatively, valve bore 4 can also be formed as athrough hole. In accordance with embodiments of the present invention, aplurality of valve bores 4 can be formed in parallel, and, it is in thisconnection that the illustrated valve bore 4 will be describedhereinafter.

In a molded pocket 5 formed starting from top side 2 a of pilot controlhousing 2, which is made of plastic, for example, a solenoid 6 isintroduced such that its central through hole coincides with valve bore4. Solenoid 6 is contacted with an electrical interface.

A valve cartridge 8 is introduced from side face 2 c, or, in otherwords, from its primary side, into valve bore 4 and is fastened to sideface 2 c. In this way, it fixes solenoid 6, which was introduced fromabove, in vertical direction, meaning that it acts as a splint member;in addition, solenoid 6 is also fixed by other bearing points in thesurrounding housing. From its primary side 8 a, which is shown on theright in FIG. 1, valve cartridge 8 is pressurized with compressed air,for example, via a compressed air duct 9 extending in vertical directionthrough pilot control housing 2, and at its secondary side 8 b, on theleft in FIG. 1, it discharges compressed air via at least one furthercompressed air duct 9 extending in vertical direction through pilotcontrol housing 2.

Valve cartridge 8 is provided with a primary valve 10 and a secondaryvalve 11. In this embodiment, primary valve 10 is designed as a 2/2-wayvalve having one passing and one blocking position. Secondary valve 11is designed as a 3/2-way valve, and it has an air admission or controlpressure position and a venting position. In the air admission position,the compressed air arriving from primary valve 10 is discharged at anair admission output 12 a, for example, for admission of air to aconnected pressure cylinder of a wheel brake. In the venting position,first output 12 a is in communication with a venting output 12 b.

Primary valve 10 has a primary armature 10 a with a diameter of 8 mm,for example, which valve is guided in axial direction in a magneticallynon-conducting armature guide tube 10 b made of brass or non-magneticsteel, for example, and is pre-loaded by an armature spring 10 c intoits open position, in which primary armature 10 a is, therefore, notbearing on its primary valve seat 13.

Analogously, secondary valve 11 has a secondary armature 11 a with adiameter of 6 mm, for example, which valve is guided in a magneticallyconducting armature guide tube 11 b, which is constructed in one piecetogether with core 15 and is advantageously joined rigidly to primaryarmature guide tube 10 b. Secondary armature 11 a is pre-loaded by anarmature spring 11 c and it cooperates with a first valve seat 14 a forfirst output 12 a and with a second valve seat 14 b for second output 12b; in the design shown in the drawings, this valve seat 14 a is alwaysable to be open.

The magnetic flux through solenoid system 6 passes through botharmatures 10 a, 11 a and common core 16 of magnetically conductingmaterial formed between them. Anti-sticking elements 17 can be disposedbetween core 16 and armatures 10 a, 11 a, which ensure earlier drop-outat higher currents, for example by pressing into core 16 or pressingagainst armatures 10 a, 11 a. For this purpose, an anti-sticking element17, in the form of a bush acting as a spacer, for example, is providedbetween secondary armature 11 a and core 15, while an air gap thatdiverts the magnetic flux passing through primary armature 10 a radiallyoutward can be formed between core 15 and primary armature 10 a.

Both armatures 10 a, 11 a are displaced by common solenoid system 6,which, for this purpose, can be de-energized or else energized with afirst lower current intensity or a second higher current intensity.Consequently, three switched positions are obtained:

(i) a de-energized home position, in which primary valve 10 is open, airadmission port 12 a of secondary valve 11 is left open and vent port 12b is shut off;

(ii) a position during energization with the first lower currentintensity, in which only primary armature 10 a is displaced and primaryvalve 10 is therefore closed; the spring force of primary armaturespring 10 c and the response of the rest of the valve system aretherefore designed such that this system is already displaced at thefirst current intensity, whereas secondary armature spring 11 c stillholds secondary armature 11 a; thus, vent port 12 b continues to be shutoff, and, so, the pressure in air admission port 12 a is held; and

(iii) a position during energization with the second higher currentintensity, in which primary valve 10 continues to be closed andsecondary armature 11 a is also displaced, such that secondary valve 11places air admission port 12 a and vent port 12 b in communication; inthis way, venting can take place between air admission port 12 a andvent port 12 b.

The air therefore flows through an air inlet 19 into the primary valve,past (or through) primary armature 10 a and, during air admission, or,in other words, de-energized condition and open primary valve 10 a, pastvalve seat 13 into a central air bore 22 of core 15, from there intosecondary valve 11, through secondary armature 11 a, past valve seat 14a and into air admission port 12 a.

As one example, core 15 is joined to primary armature guide tube 10 b(e.g., of brass) by adhesive bonding and flanging, or, as anotherexample, is joined to armature guide tube 10 b via seals. Secondaryvalve seats 14 a,b are joined to core 15 by flanging or by seals, forexample. As a result, a valve cartridge 8 containing the housed movableparts is formed.

A stepped body 18 is obtained, which houses armatures 10 a, 11 a and, onthe primary side, has a cylindrical region 18 a with larger diameterand, toward the left on the secondary side, has a cylindrical region 18b, 18 c with smaller diameter, so that it can be introduced intosolenoid 6 or the through hole thereof, thus fixing it. Primary armaturespring 10 c is housed in larger region 18 a and secondary armature 11 cin narrower region 18 b. A middle region 18 c, which is located withinsolenoid system 5, is formed continuously with narrower region 18 bhousing secondary armature spring 11 c.

According to FIG. 1 and FIG. 2, o-ring seals 20 are disposed externallyon valve cartridge 8 in the transition from region 18 a to region 18 c,externally at the front end on valve seat 14 b, and internally on core15 or secondary armature guide tube 11 b.

Valve cartridge 8 can, therefore, be introduced from side face 2 c ofpilot control housing 2 into valve bore (blind bore) 4, thus, alreadyfixing solenoid system 6.

Since valve cartridge 8 is inherently matched as regards tolerance, onlyrough fixation is needed in axial direction, and this is ensured bymolded pocket 5. The force built up when the internal pressure faces arepressurized for the first time pushes valve cartridge 6 against thehousing stop, where it remains by virtue of friction due to the diverseo-rings of the static seals.

The force and stroke tolerances of valve cartridge 8 can be easilyadjusted.

For the switching thresholds, the force tolerance of armature springs 10c, 11 c, and, especially, of primary armature spring 10 c, is the mostimportant factor. The valve seat and armature guide tube of the primaryside are sealingly joined to one another. The position of the joint canbe found as a function of force. Thus, the armature spring force can besimply adjusted in the on-going process.

Subsequently, the armature guide tube and core 15 are joined to oneanother, for example by flanging.

In this way, therefore, the stroke and force of the primary side areadjusted.

On the secondary side, an adjustment can be achieved by

-   -   an adjustment to a specified spring force,    -   adjustment of a specified stroke.

1. A two-stage solenoid valve for an electropneumatic valve controlunit, especially a pilot control unit of a pressure modulator, whereinthe solenoid valve is provided with at least: a solenoid system (6),which can be energized with a first and second current intensity, and asolenoid valve device (8) housed in the solenoid system (6) and having aprimary side (8 a) for connection to at least one first compressed airport and a secondary side (8 b) for connection to at least one secondcompressed air port, wherein there is provided on the primary side aprimary valve (10) having a displaceable primary armature (10 a)pre-loaded by a primary armature spring (10 c) for bearing on at leastone primary valve seat (13), wherein there is provided on the secondaryside a secondary valve (11) having a displaceable secondary armature (11a) pre-loaded by a secondary armature spring (11 c) for bearing on atleast one secondary-valve seat (14 b), wherein: the solenoid valvedevice (8) is designed as a valve cartridge (8) to be introduced fromone side.
 2. The solenoid valve according to claim 1, wherein a diameterof a front region (18 b) of the valve cartridge (8) relative to theintroduction direction is smaller than or equal to the diameter of arear region (18 a) of the valve cartridge (8) relative to theintroduction direction.
 3. The solenoid valve according to claim 1 or 2,wherein a diameter of a rear region (18 a) of the valve cartridge (8)relative to the introduction direction is larger than or equal to thediameter of a middle region (18 c) of the coil of the valve cartridge(8).
 4. The solenoid valve according to claim 2 or 3, wherein the rearregion (18 a) has a larger diameter than the front region (18 b) and themiddle region (18 c) has a diameter larger than or equal to that of thefront region (18 b).
 5. The solenoid valve according to one of claims 2to 4, wherein: the valve cartridge (8) has a stepped body (18)comprising the rear broader region (18 a) and at least one narrowerregion (18 b,c), which is cylindrical, for example, a narrower frontregion (18 b) houses the front armature spring (11 c), a narrower middleregion (18 c) houses each of the front and rear armatures (11 a, 10 a)at least partly and is provided for introduction into the solenoidsystem (6), and the rear broader region (18 a) houses the rear armaturespring (10 c).
 6. The solenoid valve according to claim 5, wherein thevalve seats (13, 14 a,b) of the front side and of the rear side arejoined to the stepped body (18), for example by flanging and/or caulkingand/or welding.
 7. The solenoid valve according to claim 5 or 6, whereinan armature guide tube (10 b) of the rear armature (10 a) is housed atleast partly in the middle, narrower cylindrical region (18 c).
 8. Thesolenoid valve according to one of the preceding claims, wherein thefront armature (11 a) has a smaller cross section than the rear armature(10 a).
 9. The solenoid valve according to one of the preceding claims,wherein the primary valve (10) and the secondary valve (11) have acommon core (15).
 10. The solenoid valve according to claim 9, whereinthe common core (15) is formed in one piece.
 11. The solenoid valveaccording to one of the preceding claims, wherein the secondary valve(11) is disposed at the front in introduction direction and the primaryvalve (10) is disposed at the rear in insertion direction.
 12. Thesolenoid valve according to one of the preceding claims, wherein theprimary side (8 a) is provided for a compressed air port for supplyingcompressed air, and the secondary side (8 b) is provided for dischargingcompressed air.
 13. The solenoid valve according to claim 12, whereinthe primary valve (10) is designed as a 2/2-way valve.
 14. The solenoidvalve according to claim 12 or 13, wherein the secondary valve (11) isdesigned as a 3/2-way valve.
 15. The solenoid valve according to claim14, wherein the secondary valve (11) has a first output (12 a) for acontrol pressure port or air admission port and a second output (12 b)for a vent port.
 16. The solenoid valve according to claim 15, wherein:in the de-energized condition, the primary valve (10) is open and thesecondary valve (11) leaves the air admission port (12 a) open and shutsoff the vent port (12 b), at a first lower current intensity, theprimary valve (10) is closed and the secondary valve (11) leaves the airadmission port (12 a) open and shuts off the vent port (12 b), and at asecond higher current intensity, the primary valve (10) is closed andthe secondary valve (11) releases the vent port (12 b) and leaves theair admission port (12 b) [sic: (12 a)] open, so that these are incommunication with one another for venting.
 17. The solenoid valveaccording to one of the preceding claims, wherein the valve cartridge(8) can be introduced into a blind bore (4) of the surrounding mainhousing (2).
 18. The solenoid valve according to one of the precedingclaims, wherein the valve cartridge (8) is introduced with its secondaryside into the blind bore (4) and can be fixed in the blind bore by theinitial pressurization.